Is it safe to drive with P0325?

For a short time, yes. But using lower-octane fuel than recommended while the knock sensor is offline is risky since the computer cannot detect or respond to detonation.

Will fixing P0325 restore my lost power?

Yes. Once the sensor is working, the PCM removes the conservative timing retard and power returns to normal.

Why is the knock sensor under the intake manifold on some engines?

Centering the sensor on the block gives it the best sensitivity to vibration from all cylinders. Unfortunately that location is underneath the intake manifold on many V-type engines.

Codes › P0325

P0325: The knock sensor circuit on Bank 1 has a fault

Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

Moderate severityCan you keep driving?

Yes, you can drive for now, but get it fixed soon. Without a working knock sensor, the PCM cannot detect engine knock and retards timing as a precaution, which costs you power and fuel economy.

What it means

The knock sensor listens for the high-frequency vibration signature of detonation, which is uncontrolled combustion in the cylinder. When it hears knock, it signals the PCM to retard ignition timing until the knock stops. P0325 means the PCM detected an open, short, or out-of-range resistance in the knock sensor circuit, not that knock is currently happening. With the sensor offline, the computer cannot detect actual knock, so it defaults to a safe, conservative timing map. The engine will run more conservatively, but you are also driving without the protection that sensor provides.

Common causes

Failed knock sensorThe piezoelectric element inside the sensor degrades over time. Most common on engines past 100,000 miles.
Damaged or corroded knock sensor wiring harnessThe harness runs near the block and can chafe, especially after engine work disturbs the routing.
Loose knock sensor mountingThe sensor must be torqued to spec. A loose sensor outputs incorrect signals or no signal at all.
Failed PCM input channel for the knock sensorRare. Rule out the sensor and wiring first.

What it costs

Wiring or harness repair$80 to $250
Knock sensor replacement$150 to $400 installed
Knock sensor under intake manifold (some V6/V8 engines)$300 to $700 installed due to intake removal labor

Symptoms

Check engine light on, steady
Noticeable reduction in power and throttle response
Worse fuel economy
Usually no audible knock (but the sensor cannot confirm it either way)

What to do next

The knock sensor on some engines, particularly GM V6 and V8 engines, is located under the intake manifold. The replacement cost is mostly labor for the manifold pull. On other engines it is accessible in minutes. Before buying a sensor, inspect the wiring and connector at the sensor. A broken harness clip or chafed wire is a cheaper fix. Always torque the new sensor to spec: under-torqued sensors generate false signals.

Lewis shows live ignition timing data so you can see how much the PCM is retarding timing as a result of this fault. Download Lewis.

Related codes

FAQ

Is it safe to drive with P0325?: For a short time, yes. But using lower-octane fuel than recommended while the knock sensor is offline is risky since the computer cannot detect or respond to detonation.
Will fixing P0325 restore my lost power?: Yes. Once the sensor is working, the PCM removes the conservative timing retard and power returns to normal.
Why is the knock sensor under the intake manifold on some engines?: Centering the sensor on the block gives it the best sensitivity to vibration from all cylinders. Unfortunately that location is underneath the intake manifold on many V-type engines.